Spin Hall Effect

Researchers from MIT discovered that under a powerful magnetic field and at very low temperatures, graphene can filter electrons according to the direction of their spin. This is something that cannot be done by any conventional electronic system - and may make graphene very useful for quantum computing.

it is known that when a magnetic field is turned on perpendicular to a graphene flake, current flows only along the edge, and in one direction (clockwise or counterclockwise, depending on the magnetic field orientation), while the bulk graphene sheet remains insulating. This is called the Quantum Hall effect.

Researchers from Tohoku Univeristy generated a new kind of magnetoresistance in a system with an insulating magnet. They call this new phenomenon Spin Hall magnetoresistance (SMR). In SMR, the current does not need to pass through a magnet. The researchers developed a system in which a normal metal is put in contact with a magnetic insulator. The resistance of the normal metal is influenced by the magnetization in the insulating magnet even though none of the charge current is able to pass through the magnet.

The SMR effect is a result of spin current being able to flow from the metal into the magnetic insulator. The rate of this spin transfer depends on the magnetization direction of the insulator. The more spin current passing across the metal-insulator interface, the weaker the charge current flowing through the metal.

Durham University spun-off a new company called Rhomap to develop manufacture-to-order scientific instrumentation for high precision magneto-transport measurement systems. Rhomap's instruments targets new materials and next generation semiconductors, photovoltaics, spintronics and ferromagnetic systems.

The new Ohmpoint Measurement System is a flexible research tool that offers a range of software selectable sample connection probe geometries in one system. The instrument allows users to measure resistance in two or four point geometry, sheet resistance and magneto-transport behavior, including Hall effect and magnetoresistance. The flexibility of the system also enables the user to easily select between individual measurements and batch scanning of multiple samples.

Plures Technologies announced that it will merge with CMSF Corporation, a publicly traded company with no significant operations. This means that the Plures will become a public company (OTCBB:CMSF). The public company will be called Plures Technologies. Plures main business it its 95% stake in Advanced MicroSensors Corporation (AMS). AMS is a semiconductor foundry, which develops and fabricates MEMS and spintronics solutions.

AMS's magnetic sensor product line uses magnetoresistive (AMR, GMR) materials and magnetic tunnel junctions (MTJs). According to the company, their sensors exhibit excellent performance, and they outperform traditional Hall Effect devices with regard to size, power, sensitivity, accuracy and resolution.

There's a free discussion meeting in London, UK, about Spintronics. It will take place at 28-29  September 2009, at The Royal Society, London. Here's what the organizers say:

Recent advances in generating, manipulating and detecting spin-polarized electrons promise entirely new classes of spin based sensor, memory and logic devices, generally referred to as the field of spintronics.

These advances are based on recent fundamental discoveries involving spin polarized current in novel nano-materials, including, giant tunnelling magnetoresistance, the spin Hall effect, and the excitation of magnetization via the transfer of spin angular momentum from spin polarized current.

Physicists in the US are the first to detect the spin Hall effect at room temperature, in what could be an important development in the quest for a practical source of spin-polarized electrons for spintronic devices.

David Awschalom and colleagues at the Center for Spintronics and Computation at the University of California, Santa Barbara observed the current-induced spin-polarization of electrons and the spin Hall effect in thin surface layers of ZnSe.

The 'spin Hall' is a spin current flowing in a transverse direction to the charge current in a non-magnetic material and in the absence of an applied magnetic field. The result is a measurable accumulation of “spin up” and “spin down” electrons at opposite edges of the conducting channel.